Ya sometimes it feels like we do things just because we can, without stopping to ask ourselves if we should.
I'm definitely pro-body cameras because I think it protects both the officer and the population having their interactions recorded and auditable. I can see the reason why police might want facial recognition integrated with those cameras, but I also think it takes things into a creepy direction that undermines citizen's rights.
For example, you have the right to not identify yourself to an officer except in certain situations where you do have to identify yourself (traffic stops due to traffic laws, if you're the suspect of an active investigation to name a couple). With facial recognition built into their body cameras, paired with some kind of HUD, it would circumvent your right to refuse to identify yourself by identifying you automatically. I have to question what the officers would really get out of it that would be worth giving that up.